Exercise your mind with the challenging problem sets at Project Euler. Designed to provide a fun way to introduce new concepts , the frequently asked questions section of Project Euler has this to say about the nature of the project:

Put some Photoshop wizardy at your fingertips with photo manipulation site PhotoFunia. Take a clean headshot of yourself or the soon-to-be-victim of your prank and upload it to PhotoFunia. There are currently sixty nine photos that faces can be pasted into ranging from the Andy Warhol-esque art gallery scene featured…

When keeping a blog is too much work but you want to share goofy internet video clips, pictures, and links with your friends easily, webapp Internet is Fun might be the ticket. Sign up for a free account at Internet is Fun to forward links onto friends and see the most popular items overall, and how they traveled…

We're not exactly clear on why there's a panda on Flickr puking a rainbow of photos, but there it is, an unusual way to see the best images on the photo-sharing site. Click on a photo quick before it disappears to see its Flickr page. [via]